Reconfigurable optical add/drop multiplexers (ROADMs) perform routing, adding, and dropping of optical signal in an optical line system. A ROADM can switch traffic of a wavelength-division multiplexing (WDM) system at the wavelength layer. For example, the ROADM can add, drop, or route individual or multiple wavelengths carrying data without the need to convert the optical signals from the optical domain to the electronic domain and back.